To prove this result, we introduce concentration functions to characterize the model matrices.
In [1]}, given an arbitrary matrix \(\mathbf {A}\in \mathbb {C}^{M \times N}\)  and a positive integer \(k \le N\) , the function \(\rho \)  is defined as
\(\rho _\mathbf {A}^{(k)} := \max _{\ell \in \lbrace 1,2,\dots , M\rbrace } \max _{\Omega \in \Omega _k^N} \Vert \mathbf {a}_{\ell _\Omega }\Vert _2^2,\) 
